To replace all instances of "<br>" with a new line character in a specific cell:

1. Select the cell that contains the text you want to replace.
2. In the formula bar at the top of the screen, type the following formula:
   
   
   Formula:

   =SUBSTITUTE(A1,"<br",""&CHAR(10)&"") 

   Note: Replace "A1" with the cell reference of the cell you want to modify.
3. Press Enter on your keyboard.

To replace all HTML tags in your workbook with a new line character inside the same cell:

1. Press Ctrl + H on your keyboard to open the Find and Replace dialog box.
2. In the "Find what" field, type "<*" (without the quotes).
3. In the "Replace with" field, type ""&CHAR(10)&"" (without the quotes).
4. Click the "Options" button to expand the dialog box.
5. Under "Search", select "Workbook" to search all sheets in your workbook.
6. Under "Within", select "Sheet" to search within each cell.
7. Click "Replace All" to replace all instances of HTML tags with a new line character in your workbook.

Note that this will modify all cells in your workbook that contain HTML tags, so make sure to save a backup copy of your workbook before proceeding.